Comment 6 for bug 483928

I believe I've encountered the same or similar ssh-keyscan problem.
local ssh - OpenSSH_5.1p1 Debian-5, OpenSSL 0.9.8g 19 Oct 2007
remote ssh - OpenSSH_4.3p2, OpenSSL 0.9.8e-fips-rhel5 01 Jul 2008
The remote server was having "problems": 1) no connection; 2) connection and key returned; or 3) connection but hanging until remote time out and
disconnect. With the latter, ssh-keyscan aborted immediately with exit-code=255 (see attachment).

I disagree with the original poster in that I think that ssh-keyscan should continue in all cases except for an internal error. In our case, ssh-keyscan is buried several layers deep in wrapper scripts where it is being fed (today) 3690+ host names. Per the man pages, I was expecting it to continue regardless of what the remote servers did or didn't do.